The Age of Science and Reason
From 1000 B.C to the 4th C A.D (also described as India's rationalistic period) treatises in astronomy, mathematics, logic, medicine and linguistics were produced. The philosophers of the Sankhya school, the Nyaya-Vaisesika schools and early Jain and Buddhist scholars made substantial contributions to the growth of science and learning. Advances in the applied sciences like metallurgy, textile production, scientific method, and dyeing were also made.

As keen observers of nature and the human body, India's early scientist/philosophers studied human sensory organs, analyzed dreams, memory and consciousness. The best of them understood dialectics in nature - they understood change, both in quantitative and qualitative terms - they even posited a proto-type of the modern atomic theory.

Philosophers like Pythagoras and Herodotus read the Upanishads and learnt geometry. Pythagoras - the Greek mathematician and philosopher who lived in the 6th C B.C was familiar with the Upanishads and learnt his basic geometry from the Sulva Sutras. (The famous Pythagoras theorem is actually a restatement of a result already known and recorded by earlier Indian mathematicians). Later, Herodotus (father of Greek history) was to write that the Indians were the greatest nation of the age. Megasthenes - who travelled extensively through India in the 4th C. B.C also left extensive accounts that paint India in highly favorable light (for that period).

Scientific exchanges between Greece and India were mutually beneficial and helped in the development of the sciences in both nations. By the 6th C. A.D, with the help of ancient Greek and Indian texts, and through their own ingenuity, Indian astronomers made significant discoveries about planetary motion. An Indian astronomer - Aryabhata, was to become the first to describe the earth as a sphere that rotated on it's own axis. He further postulated that it was the earth that rotated around the sun and correctly described how solar and lunar eclipses occurred.

Because astronomy required extremely complicated mathematical equations, ancient Indians also made significant advances in mathematics. Differential equations - the basis of modern calculus were in all likelihood an Indian invention (something essential in modeling planetary motions). Indian mathematicians were also the first to invent the concept of abstract infinite numbers - numbers that can only be represented through abstract mathematical formulations such as infinite series - geometric or arithmetic. They also seemed to be familiar with polynomial equations (again essential in advanced astronomy) and were the inventors of the modern numeral system (referred to as the Arabic numeral system in Europe).

The use of the decimal system and the concept of zero was essential in facilitating large astronomical calculation and allowed such 7th C mathematicians as Brahmagupta to estimate the earth's circumferance at about 23,000 miles - (not too far off from the current calculation). It also enabled Indian astronomers to provide fairly accurate longitudes of important places in India.

The science of Ayurveda - (the ancient Indian system of healing) blossomed in this period. Medical practitioners took up the dissection of corpses, practised surgery, developed popular nutritional guides, and wrote out codes for medical procedures and patient care and diagnosis. Chemical processes associated with the dying of textiles and extraction of metals were studied and documented. The use of mordants (in dyeing) and catalysts (in metal-extraction/purification) was discovered.

The scientific ethos also had it's impact on the arts and literature. Painting and sculpture flourished even as there were advances in social infrastructure. Universities were set up with dormitories and meeting halls. In addition, according to the Chinese traveller, Hieun Tsang, roads were built with well-marked signposts. Shade trees were planted. Inns and hospitals dotted national highways so as to facilitate travel and trade.